Automatic switch for telephone systems.



K. E. ERlCSSON & G. W. DAHLsTR'dM. AUTOMATIC SWITCH FOR TELEPHONE SYSTEMS.

APPLlCATlON FILED JULY16,1913.

Patented Jan. 25, 1916.

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r srrrrns mama @EWTQE KNUT ERIC ERICSSON. 0F SALTSJtj-STORANGEN, AND GUSTAF WILHELM DAHLSTRM, 0F STOCKHOLM, SWEDEN.

AUTOMATIC SWITCH. FOR TELEPHONE SYSTEMS.

Specification of Letters Patent.

Patented Jan. 25, 11916.

Application filed July 16, 1913. Serial No. 779,350.

I To all whom it may concern: i

Be it known that we, Kxii'r Einc ERICSSON and GUSTAF lVILHELM Duins rni'ni, citizens of Sweden, residing, respectively, at Saltsjo- Storiingen and Stockholm, Sweden, have invented certain new and useful Improvements in Automatic Switches for Telephone Systems, of which the following is a specification.

This invention relates to an arrangement for automatic switching in telephone systems, and in such manner that as soon as the speaking currents flow in the one direction, no reaction from said currents upon the apparatus belonging to the same station can take place.

The invention is of particular importance in telephone systems with magnifier-s, where reactions of this kind easily produce disturbing sounds.

The invention is particularly characterized by the telephone currents, arriving from one direction, themselves directly or indirectly acting upon a relay, which effects the switching. As soon therefore, as speech from either station has continued for a certain timewhich easily can be made so rents-act upon a nonpolarized relay, which,

directly effects the coupling, or else such that said first named relay only efiects a breaking at a contact point in a local circuit, in which a second relay acting upon the switch is coupled, and in this latter case, the currents acting upon the, first named relay can either be alternating or undulating cur;

rents. In such case, where the arrangement is used in connection with magnifier-s, it is preferable to use the intensified currents from said magnifiers to actuate the switch. A few embodiments of the invention are shown on the annexed drawings, where- Figure 1 shows diagrammatically a stathe line 1),, an

tion with magnifiers arranged for disconnection of the one magnifier; Fig. 2 corresponding diagram for one-hall of a station, arranged for disconnecting. Figs. 3 and 4 show modifications oi the arrangement in Fig. 1.

In Fig. l, L, and L are the two lines com prising two wires or branches, through which speaking currents alternately arrive to the magnifier station. The current from L passes first through a switch (4,, 7),, 0,, which normally has such position that (1, makes contact with 1),, whereby the current mustpass through the magnifier telephone it, and back through the other branch of the line L,. The microphone m, of the magnifier is inserted ina local circuit, which also embraces the primary winding at two transformers y), and 13. The secondary winding of the first named of these, through the relay-electromagnet E actuates, as will be later more fully described, the local circuit for the time-relay'R, with the result, that on this side of the station, the switch 0,, 7),, 0 after a short interval is reversed so that (1 makes contact with 0 instead of with 1),, against which it normally abuts. As soon as this reversal is accomplished, currents can be induced in the secondary windings of the other transformer r, and flow out in the linewire L Currents that arrive through this line under these conditions, however, can only circulate through the transformer 1' and the line itself, unable to affect any magnifier, or thereby the line L,. Neither can currents induced in the magnifier 7a, m, and t *ansformer r, in any manner affect the line L, through the magnifier in, m whereby otherwise disturbing sounds could be pr0- duced.

\Vhen speech through the line L, ceases, the switch. a 1),, 0,, actuated by its timerelay, returns to the normal position with a, in contact with 7),. It now speaking currents arrive through the line L these will induce magnified currents through the magnifier h, m which in turn affect both the transformer 7 orcducing currents through d also the transformer 72,, whereby through a time-relay, in the inanner similar to that just described, the switch a, I), c, is reversed, preventing currents that may then arrive through the line L, from 1,, fed from the secondary windings of the transformers y), and y), respectively, and actuating the electromagnet IQ. as also the circuit L is shown in Fig. 1. \Vires such as Z and I connect each of the transformers 2),, p, with an electromagnet E the armature of which is in the shape of a diaphragm M, and carries an arm A, which latter can be arranged so that the amplitudes of the vibrations of its free end are greater than that of the diaphragmfor instance by fixing the arm both to the cente' and edge of thediaphragm, as shown in the figure. At the free end of the arm is a contact piece K, against which rests one end of a lever ll, counterbalanced by the weight V.

Details of the mechanism just described may be 'aried at will without departing from the spirit of my invention.

The diaphragm M, A, and lever H form part of a local circuit which includes the time-relay previously mentioned, and said relay, in its construction as shown, involves also a mo able core J in aforesaid solenoid, further a counterweight (1 connected totho core J by means of a flexible band led over a pulley D, and in a manner tending to raise the said core, and finally a shoulder N upon the core J, which actuates the switch a, b, e, or (1 7), (2 generally designated by a, I), c, previously described. Under influence of the normally closed circuit through the. battery B etc. the core J is normally held down so that the shoulder N presses the. arm (1, against the contact I). \Vhen, however, the diaphragm M begins to vibrate and make the contact between K and 1-1 intermittent, the attraction of the solenoid R R upon the core J generally becomes sulliciently reduced to enable the counterweight G to lift the core so as to permit the arm afor the purpose here supposed to be rcsilientto rise and press against the upper contact 0. The inertia of the movable parts J, G, etc., can of course easily be ad-' justed so that the reversal takes place in a suitable interval of time, that is an interval such that nothing essential of the speech is lost, and such that short pauses in the speech-fol instance less than 0.5l second, will not cause a reversal of the switch.

The core J should be suflieiently mobile to enable its shoulder N, during normal speech, to rise higher than the position actually required for contact between the arm a and. the upper contact 0. This is of impor- .bring it into continual oscillation. I 'this'method of adjus ing themass of'the tance in order that minor irregularities in the speech, which may tend to 'lower the core, should not cause an interruption between a and 'c; on the other hand the mobility of the core must not be such as to Besides ,core and counte weight etc. in suitable relation to the act/1V6 forces, a frictional resistance can be introduced in order to reduce the mobility of the parts. For this purpose, as for instance l1()\\'11 in the flexible band connecting core and counterweight, besides being led over the pulley I), can be arranged to pass over two fixed rods or pins F, which eventually could be adjustable. for the purpose of reguhtion, but of course any other device with the object in view can be used. It should be clearly understood, that such an alternative arrangement of the timerelay and local circuit can be made or used, whereby the latter is normally open instead of closed, when the former in inert condition will press the arm (4 against the contact I). In such case thevibrations of the diaphragm M will intermittently close the circuit at the point of contact of the parts it and 1-1, when the core J, will be attracted by the solenoid 11 with suflicient average strength to eii'ect the reversal of the switch.

In the arrangement as shown diagrammatically in Fig. 2 and supposed to correspond to one half of that in Fig. 1with corresponding parts,,similarl v lettered, but without indicesthe switch is arranged in a somewhat different manner, besides which the connections are such that the magnifier is short-circuited instead of being cut out. The result of this remains the same as in Fig. 1. The incoming line to the switch is here connected with a member a, carrying a contact piece for a sliding-contact, which latter in turn is connected with the contact 7). The sliding-contact is held by the tinierelay normally in its upper position and rests then against a contact arm (I, which by means of a spring or simila' arrangement tends to move downward. The cur rents arriving through the line L, will then pass the telephone apparatus it of the magnifier, while the transformer r is shortcircuited. When on the other hand the time-relay is affected in the manner.previously described, it will permit the slidingcontact to drop, and with it the arm (1, so far that the latter comes in contact with c. The sliding-contact continues further until the contact 0 is freed from the arm (I, and from here then the connections are such that the transformer r is in circuit, while the telephone apparatus it is short-cireuited.

In Fig. 25 the switch is .of the same type as in Fig. 1. but otherwise the connections are so altered, that the same primary winding is used for the transformer r which transmits speaking currents to thenne, as also for the transformer '79, which'serves' the time-relay. In Fig. 4, the last'mentioned' transformer is left out altogether, and the tion and in what manner the same is to be performed, we declare that'what we claim is:

' a line switch for each line, the relay acting upon the line switch and arranged to switch each line so as to allow the speaking currentsto flow in the one or the other direction only, an auxiliary circuit for each line,

' amagnifier associated with eachline for connecting each auxiliary circuit to the other line circuit so as to obtain magmfi ed speaking currents in'the said auxihary circuits, and intermediate means between the switch relay of one line and the said auxil- ,iary circuit of the other line for operating said relay of one line by the said magnified currents from the magnifier of the other station.

2. In a telephone repeating'system in combination, two lines each adapted to either send or receive, a switch relay for each line, a'lifie switch for each line, each relay acting upona line switch and arranged to'switch eachjline so as to allow the speaking currents to flow in one or the other direction only, an auxiliary circuit for each line, a magn acuitto' the other line circuit so as to obtain magnifiedspeaking currents in the said auxihary c rcuit, and intermediate means be- "'.tween theswitch relay of one line and the 'said auxiliary circuit of the other line for operating said. relay of one line by the aid of the magni ed currents from the magnifier of the. other li e, said auxiliary circuit being inductively connected to the relay.

"a telephone repeating system in ifier for connecting each auxiliary circombination, a receiving line, a sending line, an auxiliary circuit for each line, a magnifier for each line, a line switch for each line, means for operating said switch for one line by the magnifier for the other line, said line switch short circuiting the magnifier of its own line in one of its positions.

4;. In, a telephone repeating system in combination, a receiving line, a sending line, an auxiliary circuit for the sending line, a line switch for each line,- a magnifier for each line, a switch relay, said relay being adapted to operate a line switch, means for operating said relay by the aid of the magnified currents of the other line, a transformer for said sending line, said line switch short circuiting the magnifier of'the seITding line in one position, and short c'ircuiting the secondary of said transformer in its other position, the primary of said transformer being inserted in the magnifier circuit of the other'line.

5. In a telephone repeating system in combination, a sending line, a receiving line, switch for each line, a magnifier for each line, two transformers for eachline, an interrupter for each line, and a switch relay for' each line, the secondary of one of the said transformers being in circuit With said interrupter, each of said line switches connecting the secondary of the remaining transformer of the other line with the two branches of its own line, and said switch simultaneously short circuiting the magnifier of its own line.

In testimony whereof we have aflixed our signatures.

KNUT ERIC ERICSSON. GUSTAF WILHELM DAHLSTRllM. 

